Anti-tuberculosis drug resistance in Bangladesh: reflections from the first nationwide survey.

OBJECTIVE: To determine the prevalence of tuberculosis (TB) drug resistance in Bangladesh. DESIGN: Weighted cluster sampling among smear-positive cases, and standard culture and drug susceptibility testing on solid medium were used. RESULTS: Of 1480 patients enrolled during 2011, 12 falsified multidrug-resistant TB (MDR-TB) patients were excluded. Analysis included 1340 cases (90.5% of those enrolled) with valid results and known treatment antecedents. Of 1049 new cases, 12.3% (95%CI 9.3-16.1) had strains resistant to any of the first-line drugs tested, and 1.4% (95%CI 0.7-2.5) were MDR-TB. Among the 291 previously treated cases, this was respectively 43.2% (95%CI 37.1-49.5) and 28.5% (95%CI 23.5-34.1). History of previous anti-tuberculosis treatment was the only predictive factor for first-line drug resistance (OR 34.9). Among the MDR-TB patients, 19.2% (95%CI 11.3-30.5; exclusively previously treated) also showed resistance to ofloxacin. Resistance to kanamycin was not detected. CONCLUSION: Although MDR-TB prevalence was relatively low, transmission of MDR-TB may be increasing in Bangladesh. MDR-TB with fluoroquinolone resistance is rapidly rising. Integrating the private sector should be made high priority given the excessive proportion of MDR-TB retreatment cases in large cities. TB control programmes and donors should avoid applying undue pressure towards meeting global targets, which can lead to corruption of data even in national surveys.

Analysis of immune responses and serological cross reactivities among Vibrio cholerae O1, Shigella flexneri 2a and Haemophilus influenzae b.

Antigenic determinants expressed on the bacterial cell surface are of importance in the serological characterization and microbiological diagnosis. The bacterial strains carrying these identical or similar antigenic epitopes might react with antibodies produced against other strains. In this study, strong immunogenicity and antigenic cross reactivity were demonstrated among V. cholerae O1, S. flexnerii 2a and H. influenzae b surface components. The enzyme linked immunosorbent assay (ELISA) results were supported by Western blot analysis, where at least 20 antigenic bands, were obtained in each of the reactions, when the surface components were reacted with the homologous antisera. The indirect ELISA results also demonstrated high degree of antigenic relatedness between the surface components of these species, where each surface component was reacted with the heterologous antisera. Western blot analysis also revealed cross reactions between the surface components suggesting common distribution of antigens/epitopes in these bacterial species. This study, thus, gave a clear idea of the level of antigenic sharing and variations among the pathogenic V. cholerae O1, S. flexneri 2a and H. influenzae b strains, which in future, may help in selecting a proper candidate for vaccines and immunodiagnostics development.

Toxin(s), other than cholera toxin, produced by environmental non O1 non O139 Vibrio cholerae.

A total of 39 Vibrio cholerae non O1 non O139 strains were isolated from surface waters of different parts of Dhaka City, Bangladesh. All these strains showed lack of ctx or zot gene, as demonstrated by the PCR analysis. Eighteen representative strains were tested for enterotoxin production using a rabbit ileal loop model, of which live cells of 8 strains and culture filtrates of 6 strains produced fluid accumulation in ileal loops. However, none of them produced heat stable toxin (ST), as detected by suckling mouse assay. On the other hand, 15% of isolates produced cytotoxin as detected by the Chinese Hamster Ovary (CHO) cell assay. Fifty times concentrated culture filtrates of the representative strains did not give any precipitin band against the anti-cholera toxin, suggesting the strains produced an enterotoxin, which is antigenically different from known cholera toxin (CT). Eighty percent of the total isolates were found to be positive for heat labile haemolysin detected by tube method, whereas, 39% were found positive by the Christie-Atkins-Munch-Petersen (CAMP) method. However, 87% of the isolates were positive for haemagglutinin/protease and all of the strains were positive for mannose-sensitive-haemagglutinin assay.

Visualization of binding and transcytosis of botulinum toxin by human intestinal epithelial cells.

Botulinum toxin is an unusually potent oral poison, which means that the toxin must have an efficient mechanism for escaping the lumen of the gut to reach the general circulation. Previous work involving iodination of toxin and analysis of its movement demonstrated a specific process of transepithelial transport. In the present study, botulinum toxin labeled with Alexa Fluor 488 was used to visualize the discrete steps of binding, internalization, transcytosis, and release. The data revealed that binding sites for the toxin were distributed across the apical surface of epithelial cells, and there was no evidence of significant clustering. The amount of toxin bound to receptors at saturation was too large to be accommodated in a single wave of endocytosis. Toxin that entered epithelial cells did not remain in the vicinity of the endocytosing membrane, which is in striking contrast to events in neuronal cells. Instead, the toxin began to spread across the length of cells, eventually being released on the basolateral surface. Migration of toxin through epithelial cells required redistribution to the cell periphery. This migration pattern could be attributed to the large and centrally located nucleus, which physically displaced transport vesicles. Transcytosed toxin began to reach the contralateral surface within ca. 5 min, and transcytosis was essentially complete within 20 to 30 min.

Seroepidemiology of hepatitis B and delta virus infections in Bangladesh.

Hepatitis B virus (HBV) infection is one of the most prevalent public health problems worldwide, and causes 1 million deaths annually. In Bangladesh, information about prevalence of HBV infection is scarce, and there is no available data on HDV infection. We determined rates of HBsAg and anti-HBc seropositivity in asymptomatic, healthy children (n = 181) and adults (n = 354) presenting to referral facilities in Dhaka, Bangladesh, and tested a separate group of HBsAg-positive patients (n = 180) for prevalence of HDV. Testing of serum was also performed for signs of liver disease. Overall, seropositivity of HBsAg and anti-HBc in studied subjects was 3 per cent (16/534) and 21.1 per cent (113/534), respectively. Prevalence of HBsAg was highest in the 5- to 9-year-old (8.5 per cent, 7/82) and 10- to 14-year-old (5.9 per cent, 2/34) age groups. Unlike HBsAg, prevalence of anti-HBc was lower in children (14.9 per cent in those below the age of 15) than adults (24.4 per cent in those aged 20-34 years) (p < 0.05). Most HBsAg-positive individuals were symptomatic (n = 125, 69.4 per cent). A high rate (24.4 per cent, 44/180) of simultaneous infection with HDV was observed among HBsAg-positive subjects, with higher rates in older individuals. Anti-HDV seropositivity rate was similar among asymptomatic (21.8 per cent, 12/55) and symptomatic (25.6 per cent, 32/125) HBsAg carriers. Our data suggest that Bangladesh is of moderate endemicity for HBV infection, and has relatively high rates of co-infection with HDV. Control HBV and HDV infection in Bangladesh may be best achieved by targeting preschool children, which could fit readily within the existing EPI schedule.